l Potable : 2,6%

Groundwater Flow zPorous media zAquifer Properties: yT: the rate of flow per unit width through the entire thickness of an aquifer, per unit hydr. Gradient (the more great the more permeable) yS: the volume of water released from storage (or added to it) per unit horizontal area of aquifer & per unit decline (or rise) of piezometric head, φ.

zDarcy’s Law + Continuity (mass balance) Equation = Flow Equation (φ,T,S,x,z,y,t) zAquifer’s Geometry zvalues of relevant physical coef. (K, S,...) zInitial conditions (describe the initial state of the fluid in the domain) zBoundary cond. (how the fluid interacts with its surroundings) GR Flow - The Problem

zAnalytical Methods: seldom applied zNumerical Methods (FD, FE, MOC) (Computer Revolution Aid) - Models yForecasting Problem: to obtain φ(x,y,z,t) u(x,y,z,t) GR Flow - The Solution

Hydrologic Basin of Kastoria

Geologic Map

The model’s grid

Map of Piezometric Heads

Groundwater Velocities

GW Quality Problem zQuality instead of pollution (GW already contains dissolved matter) zIncreasing Demand - Decreasing quality men drink unclean water ~~~ concentration of dissolved pollutants > standards by the World Health Org.

A.Environmental zflow through carbonate rocks - dissolved rock zsea water intrusion (disturbed equillibrium) B.Domestic zaccidental breaking of sewers zpercolation from septic tanks zrain infiltrating through sanitary landfills zBiological contaminants (bacteria+viruses) also related to this source GW Pollution Sources

C.Industrial za single sewage disposal for both ind.-resident. zWaste disposal in non-protected constructions zHeavy metals, toxic compounds, radioactive materials B.Agricultural zirrigation water or rain water dissolving and carrying fertilizers, salts, etc. as they infiltrate through surface and replenish the aquifer GW Pollution Sources

Transport Phenomenon zMass transport in porous media=the movement & accumulation of pollutants with the water in the interstices z4 mechanisms affecting transport: yconvection ymechanical dispersion ymolecular diffusion ysolid-solute interreactions, chemical reactions & decay phenomena

Dispersion zTracer gradually spreading & occupies a region>flow domain. Irreversible process ze.g. instantaneous point injection through a well, into an aquifer - spreading (longitudinal + transversal) xellipsoidal contours of equal concentration xbreakthrough curve in obs. well (C-t)

zMechanical Dispersion. Spread due to: yvarying velocity distribution in the interstice ypresence of the pore system (abnormal layout) zMolecular diffusion (low velocities) results from variations in concentr. In the liquid phase yproduction of an additional flux of pollutant particles from regions of higher C to those of lower ones zMech.Disp.+Mol. Dif.=Hydrodynamic Dispersion Dispersion: reason

GW Pollution Problem zFlow equation + transport equation zNumerical methods zh(x,y,z,t) + c(x,y,z,t) zE.G. Figure : Cases of aquifer pollution

GW Flow & Transport Mathematic Models Input Data zAquifer Geometry zBoundary - Initial Conditions zParameters yhydraulic yhydrogeologic ychemical zExternal stresses zHydraulic contact (rivers-lakes-aquifers ) ΜODEL Results values of (x,y,z) –hydraulic heads –velocities –concentrations value forecasting (x,y,z,t) aquifer’s volumetric budget